U.S. patent number 7,346,393 [Application Number 10/460,975] was granted by the patent office on 2008-03-18 for implantable cardiac rhythm management system having multiple therapy modalities.
This patent grant is currently assigned to Cardiac Pacemakers, Inc.. Invention is credited to Jiang Ding, Bruce H. Kenknight, Julio Spinelli, Yinghong Yu, Qingsheng Zhu.
United States Patent |
7,346,393 |
Spinelli , et al. |
March 18, 2008 |
Implantable cardiac rhythm management system having multiple
therapy modalities
Abstract
A cardiac rhythm management system for providing a plurality of
therapy modalities. For example, the system may include a cardiac
resynchronization therapy module for providing cardiac
resynchronization therapy and a pacemaker module for providing
bradycardia therapy, as well as a selector module coupled to the
cardiac resynchronization therapy module and the bradycardia
module. The selector module may select an operating mode from among
a plurality of operating modes including the cardiac
resynchronization therapy module and the pacemaker module. Various
manual and automatic methods may be used to select the operating
mode. In addition, a reversion management system may be included to
assist the cardiac rhythm management system to recover in case of a
disruption to the system.
Inventors: |
Spinelli; Julio (Shoreview,
MN), Zhu; Qingsheng (Little Canada, MN), Kenknight; Bruce
H. (Maple Grove, MN), Yu; Yinghong (Maplewood, MN),
Ding; Jiang (Maplewood, MN) |
Assignee: |
Cardiac Pacemakers, Inc. (St.
Paul, MN)
|
Family
ID: |
33511142 |
Appl.
No.: |
10/460,975 |
Filed: |
June 12, 2003 |
Prior Publication Data
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|
Document
Identifier |
Publication Date |
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US 20040254614 A1 |
Dec 16, 2004 |
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Current U.S.
Class: |
607/9; 607/14;
607/25 |
Current CPC
Class: |
A61N
1/3627 (20130101) |
Current International
Class: |
A61N
1/36 (20060101) |
Field of
Search: |
;607/4-28 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Auricchio et al. "Effect of Paching Chamber and Atrioventricular
Delay on Acute Systolic Function of Paced Patients with Congestive
Heart Failure." Circulation. 1999; 99: 2993-3001. cited by examiner
.
Kass et al. "Improved Left Ventricular Mechanics from Acute VDD
Pacing in Patients with Dilated Cardiomyopathy and Ventricular
Conduction Delay." Circulation. 1999; 99: 1567-1573. cited by
examiner.
|
Primary Examiner: Sykes; Angela D.
Assistant Examiner: Holmes; Rex
Attorney, Agent or Firm: Schwegman, Lundberg & Woessner,
P.A.
Claims
What is claimed is:
1. A cardiac rhythm management system comprising: a cardiac
resynchronization therapy module for providing cardiac
resynchronization therapy; a pacemaker module for providing
bradycardia therapy; sensing circuitry to collect
electrophysiological data indicating the presence or absence of a
ventricular conduction delay; a selector module coupled to the
cardiac resynchronization therapy module and the pacemaker module,
wherein the selector module is configured to select an operating
mode from among a plurality of operating modes including the
cardiac resynchronization therapy module and the pacemaker module;
wherein the pacemaker module reverts to an asynchronous pacing mode
if atrial sensing is lost; wherein the cardiac resynchronization
module reverts to an inhibited mode in which no pacing pulses are
delivered if atrial sensing is lost; and, wherein the selector
module is configured to automatically select between the cardiac
resynchronization therapy module and the pacemaker module based
upon the collected electrophysiological data indicating the
presence or absence of a ventricular conduction delay.
2. The system of claim 1, wherein the selector module is configured
to automatically select between the cardiac resynchronization
therapy module and the pacemaker module on a continuous basis.
3. The system of claim 1, wherein the selector module is further
configured to compare an interval between a beginning of an
intrinsic ventricular depolarization designated as Q* and an ending
of the intrinsic ventricular depolarization designated as S* to a
threshold in order to automatically select between the cardiac
resynchronization therapy module and the pacemaker module.
4. The system of claim 1, wherein the selector module is configured
to automatically select between the cardiac resynchronization
therapy module and the pacemaker module on a periodic basis.
5. The system of claim 1, wherein the selector module is further
configured to: detect a time of peak depolarization R in an
electrogram waveform; derive an interval between a beginning of an
intrinsic ventricular depolarization designated as Q* as the point
at which a derivative of the electrogram waveform exceeds a
specified percentage of the maximum derivative of the electrogram
waveform before R; derive an ending of the intrinsic ventricular
depolarization designated as S* as the point at which a derivative
of the electrogram waveform exceeds a specified percentage of the
maximum derivative of the electrogram waveform after the
depolarization peak; and, compare Q* and S* to a threshold in order
to automatically select between the cardiac resynchronization
therapy module and the pacemaker module.
6. The system of claim 1, further comprising a protected memory
module coupled to the selector module, wherein a plurality of
operating parameters associated with the operating mode are stored
in the protected memory module at a periodic interval.
7. The system of claim 6, wherein the periodic interval is 1
day.
8. The system of claim 6, wherein the periodic interval is 1
week.
9. A method for configuring a cardiac rhythm management system, the
method comprising programming the system to automatically: (a)
detect physiological data of an individual, including
electrophysiological data indicating the presence or absence of a
ventricular conduction delay; and (b) select an operating mode from
the plurality of modes for the cardiac rhythm management system
based on the physiological data, including selecting between a
pacemaker mode and a cardiac resynchronization therapy mode based
upon the electrophysiological data indicating the presence or
absence of a ventricular conduction delay; and programming the
system such that the pacemaker module reverts to an asynchronous
pacing mode if atrial sensing is lost, and the cardiac
resynchronization module reverts to an inhibited mode in which no
pacing pulses are delivered if atrial sensing is lost.
10. The method of claim 9, further comprising programming the
system to select between a pacemaker mode and a cardiac
resynchronization therapy mode on a continuous basis.
11. The method of claim 9, further comprising programming the
system to select between a pacemaker mode and a cardiac
resynchronization therapy mode on a periodic basis.
12. The method of claim 9, further comprising programming the
system to: detect a beginning of an intrinsic ventricular
depolarization designated as Q*; detect an ending of the intrinsic
ventricular depolarization designated as S*; measure an interval
between Q* and S*; and compare the interval to a threshold to
select the operating mode.
13. The method of claim 12, further comprising programming the
system to select a pacemaker mode if the interval is below the
threshold.
14. The method of claim 12, further comprising programming the
system to select a cardiac resynchronization mode if the interval
is equal to or above the threshold.
15. The method of claim 9, further comprising programming the
system to: detect a time of peak depolarization R in an electrogram
waveform; derive an interval between a beginning of an intrinsic
ventricular depolarization designated as Q* as the point at which a
derivative of the electrogram waveform exceeds a specified
percentage of the maximum derivative of the electrogram waveform
before R; derive an ending of the intrinsic ventricular
depolarization designated as S* as the point at which a derivative
of the electrogram waveform exceeds a specified percentage of the
maximum derivative of the electrogram waveform after the
depolarization peak; and, compare Q* and S* to a threshold in order
to automatically select between the cardiac resynchronization
therapy module and the pacemaker module.
16. The method of claim 9, further comprising programming the
system to: measure a first interval during an intrinsic systolic
cycle; measure a second interval during a stimulated systolic
cycle; and compare a percentage change in a duration between the
first interval and the second interval against a threshold to
select the operating mode.
17. The method of claim 9, further comprising programming the
system to: measure a first point of an onset of ventricular
depolarization; measure a second point of a peak of a
left-ventricular intracardiac electrogram; calculate an interval
based on the first and second points; and compare the interval to a
threshold to select the operating mode.
18. The method of claim 9, further comprising: measuring a duration
of a ventricular depolarization at a surface of the individual; and
comparing the duration to a threshold to select the operating
mode.
19. The method of claim 9, further comprising programming the
system to: measure pulse pressures in both a right ventricle and a
left ventricle; calculate a normalized pressure loop area based on
the pulse pressures; and compare the normalized pressure loop area
to a threshold to select the operating mode.
20. The method of claim 11, further comprising programming the
system to select between a pacemaker mode and a cardiac
resynchronization therapy mode on a daily basis.
21. The method of claim 11, further comprising programming the
system to select between a pacemaker mode and a cardiac
resynchronization therapy mode on a weekly basis.
22. The method of claim 9, further comprising programming the
system to perform the steps of storing a plurality of operating
parameters associated with the operating mode in a protected memory
at a periodic interval; and accessing the plurality of parameters
upon disruption of the cardiac rhythm management system.
23. The method of claim 22, further comprising setting the periodic
interval to 1 day.
24. The method of claim 22, further comprising setting the periodic
interval to 1 week.
25. The method of claim 9, further comprising programming the
system to perform the step of selecting a first mode from the
plurality of modes if a hemodynamic performance of the individual
increases through application of cardiac resynchronization
therapy.
26. A cardiac rhythm management device comprising: means for
delivering bradycardia therapy in a DDD pacing mode; means for
delivering cardiac resynchronization therapy in a VDD mode; wherein
an AV delay used for cardiac resynchronization therapy is shorter
than the AV delay used for bradycardia therapy; and means for
switching from bradycardia therapy to cardiac resynchronization
therapy based upon one or more sensed signals that indicate a
hemodynamic benefit from cardiac resynchronization therapy.
27. The device of claim 26, further comprising means for storing a
plurality of operating parameters to allow the plurality of
operating parameters to survive a disruption to the cardiac rhythm
management device.
Description
TECHNICAL FIELD
This invention relates to a cardiac rhythm management system. In
addition, the invention relates to an implantable cardiac rhythm
management system having multiple therapy modalities. Further, the
invention relates to a cardiac rhythm management system including
at least bradycardia therapy and cardiac resynchronization therapy
capabilities.
BACKGROUND
Numerous therapies have been developed to address the needs of
individuals suffering from heart diseases or abnormalities. For a
first example, individuals suffering from bradycardia, or an
abnormally slow heart rate, can be treated using a pacemaker. A
pacemaker alters the individual's heart rate to return heart rate
performance to normal levels. A pacemaker typically accomplishes
this by delivering a series of electrical impulses to the heart
tissue via one or more leads, thereby stimulating the heart tissue
to contract at a specified rate. Therefore, a primary function of
bradycardia therapy using a pacemaker is to provide rate support
for the heart.
The pacemaker typically functions as an on-demand device, meaning
that the pacemaker will function only when rate support is
necessary. The pacemaker will typically delay for a certain
duration, termed an escape interval, before providing an electrical
impulse to the heart. If the intrinsic electrical activity of the
individual's heart causes the heart to contract before the escape
interval expires, the pacemaker will not send an electrical
impulse. Instead, the pacemaker will reset the escape interval and
wait for the escape interval to expire again. Therefore, if the
individual's heart is beating at a specified acceptable rate, the
pacemaker will not provide an electrical impulse until rate support
is needed. Other functions of a pacemaker may include adaptive-rate
pacing, in which the rate of the pacing is increased or decreased
based on an individual's physiological needs.
In a second example of a heart abnormality, individuals may exhibit
a decrease in hemodynamic efficiency due to the onset of congestive
heart failure (CHF). A possible therapy for CHF is the use of a
cardiac resynchronization therapy (CRT) device. A CRT device, like
a pacemaker, can deliver a series of electrical impulses to a heart
tissue. However, a CRT device functions to synchronize the
contraction of a heart rather than to pace the heart like a
pacemaker. A CRT device may deliver a series of electrical impulses
to the heart at a set rate, usually in conjunction with each
intrinsic heartbeat, to synchronize the contraction of different
sections of the heart. Research and development into the use of a
CRT device to treat CHF has established a set of therapeutic
features that can be customized for each individual in order to
maximize hemodynamic function. For instance, methods have been
developed for optimizing the timing between electrical stimuli,
thereby providing maximum resynchronization benefits. Therefore, a
primary function of a CRT device is resynchronization, making the
timing and the delivery of each electrical impulse for each
heartbeat important.
Consequently, while bradycardia therapy focuses on rate support on
an as-needed basis, CHF therapy focuses on resynchronization.
During resynchronization, particular attention may be paid to
atrioventricular delays, and electrical impulses are typically
provided for every heartbeat. Because therapeutic priorities of
bradycardia patients differ from those of CHF patients, it is a
current practice in the industry to design different products for a
patient depending on whether a patient exhibits bradycardia or CHF.
Therefore, initial decisions must be made for each patient on
whether to implant a bradycardia pacemaker or a CHF cardiac
resynchronization therapy device.
Currently, pacemakers and CRT devices are not interchangeable, and
a pacemaker cannot be reprogrammed to be a CRT device and vice
versa. Therefore, not only must treatment decisions be made
initially, once a device is implanted into the patient, it cannot
be adapted should the patient's needs change, such as, for example,
from a need for bradycardia therapy to a need for cardiac
resynchronization therapy. Further, product development costs are
increased because separate devices must be designed.
It would therefore be desirable to develop a cardiac rhythm
management system having multiple therapy modalities.
SUMMARY
Generally, the present invention relates to a cardiac rhythm
management system. In addition, the invention relates to an
implantable cardiac rhythm management system having multiple
therapy modalities. Further, the invention relates to a cardiac
rhythm management system including at least bradycardia therapy and
cardiac resynchronization therapy capabilities.
In one aspect, the invention relates to a cardiac rhythm management
system including a cardiac resynchronization therapy module for
providing cardiac resynchronization therapy, a pacemaker module for
providing bradycardia therapy, and a selector module coupled to the
cardiac resynchronization therapy module and the pacemaker module,
wherein the selector module selects an operating mode from among a
plurality of operating modes including the cardiac
resynchronization therapy module and the pacemaker module.
In another aspect, the invention relates to a method for a cardiac
rhythm management system to select between a plurality of operating
modes, the method including: detecting physiological data of an
individual; and selecting an operating mode from the plurality of
modes for the cardiac rhythm management system based on the
physiological parameter.
In yet another aspect, the invention relates to a cardiac rhythm
management device including means for providing a first operating
mode associated with a first therapy for a heart, means for
providing a second operating mode associated with a second therapy
for the heart, and means for selecting between the first operating
mode and the second operating mode.
The above summary of the present invention is not intended to
describe each disclosed embodiment or every implementation of the
present invention. The figures and the detailed description which
follow more particularly exemplify these embodiments.
DESCRIPTION OF THE DRAWINGS
The invention may be more completely understood in consideration of
the following detailed description of various embodiments of the
invention in connection with the accompanying drawings, in
which:
FIG. 1 is a schematic/block diagram illustrating one example
embodiment of a cardiac rhythm management system coupled to a heart
in accordance with the present invention;
FIG. 2 is a graph showing atrial and ventricular depolarization as
a function of time;
FIG. 3 illustrates a plurality of modules associated with an
example cardiac rhythm management system made in accordance with
the present invention;
FIG. 4 shows an operational flow of a cardiac rhythm management
system according to an embodiment of the present invention;
FIG. 5 illustrates an operational flow of a cardiac rhythm
management system in accordance with another embodiment of the
present invention;
FIG. 6 shows an operational flow of a cardiac rhythm management
system according to an embodiment of the present invention;
FIG. 7 shows an operational flow of a reversion management
subsystem of a cardiac rhythm management system in accordance with
another embodiment of the invention; and
FIG. 8 illustrates an operational flow of a cardiac rhythm
management system including a reversion management subsystem in
accordance with an embodiment of the invention.
While the invention is amenable to various modifications and
alternative forms, specifics thereof have been shown by way of
example in the drawings and will be described in detail. It should
be understood, however, that the intention is not to limit the
invention to the particular embodiments described. On the contrary,
the intention is to cover all modifications, equivalents, and
alternatives falling within the spirit and scope of the
invention.
DETAILED DESCRIPTION
The present invention relates to a cardiac rhythm management
system. In addition, the invention relates to an implantable
cardiac rhythm management system having multiple therapy
modalities. Further, the invention relates to a cardiac rhythm
management system including at least bradycardia therapy and
cardiac resynchronization therapy capabilities. While the present
invention is not so limited, an appreciation of various aspects of
the invention will be gained through a discussion of the examples
provided below.
The present apparatus and methods are described with respect to
implantable cardiac rhythm management (CRM) systems, such as
pacemakers, cardioverter/defibrillators, pacer/defibrillators, and
multi-chamber and/or multi-site (in single or multiple heart
chambers) cardiac resynchronization therapy (CRT) devices. Such CRT
devices are included within CRM systems even though the CRT devices
need not necessarily modulate heart rate. Such CRT devices may
instead provide contraction-evoking stimulations that establish or
modify the conduction path of propagating depolarizations to obtain
more efficient pumping of the heart. Moreover, the present
apparatus and methods also find application in other implantable
medical devices and in devices that may not be implanted including,
but not limited to, external pacemakers,
cardioverter/defibrillators, pacer/defibrillators, multi-chamber
and/or multi-site CRT devices, monitors, programmers, and
recorders, whether such devices are used for providing diagnostics,
therapy, or both.
Example CRM systems and methods are described below. The systems
and methods provided are examples only, and other systems and
methods can also be used.
I. Example CRM System
A. Components of the CRM System
FIG. 1 is a schematic/block diagram illustrating one example
embodiment of a CRM system 100 coupled to a heart 115. In this
embodiment, system 100 includes, among other components, a CRM
device 105 that is coupled by leads 110A-B to the heart 115. The
heart 115 includes four chambers: a right atrium 115A, a right
ventricle 115B, a left atrium 115C, and a left ventricle 115D. The
heart 115 also includes a coronary sinus 115E, a vessel that
extends from the right atrium 115A toward the left ventricular free
wall.
In one embodiment, the lead 110A includes an electrode associated
with the right atrium 115A, such as tip electrode 120 and/or ring
electrode 125. The electrode is "associated" with the particular
heart chamber by inserting it into that heart chamber, or by
inserting it into a portion of the heart's vasculature that is
close to that heart chamber, or by epicardially placing the
electrode outside that heart chamber, or by any other technique of
configuring and situating an electrode for sensing signals and/or
providing therapy with respect to that heart chamber. Lead 110B,
which is introduced into the coronary sinus 115E and/or the great
cardiac vein or one of its tributaries, includes one or more
electrodes associated with the left ventricle 115D, such as
electrodes 130 and 135. The device 105 may also include other
electrodes, such as housing electrode 150 and/or header electrode
155, which are useful for, among other things, unipolar sensing of
heart signals or unipolar delivery of contraction-evoking
stimulations in conjunction with one or more of the electrodes 120,
125, 130, and 135 associated with the heart 115. Alternatively,
bipolar sensing and/or therapy may be used between electrodes 120
and 125, between electrodes 130 and 135, or between one of
electrodes 130 and 135 and another closely situated electrode.
The CRM device 105 includes a sensing module 160 that is coupled to
one or more of the electrodes for sensing electrical
depolarizations corresponding to heart chamber contractions. Such
electrical depolarizations of the heart tissue include atrial
depolarizations, referred to as P-waves, and ventricular
depolarizations, referred to as QRS complexes. The QRS complex is a
rapid sequence of several signal excursions away from a baseline in
sequentially switching polarity, with the largest excursion
referred to as an R-wave. See FIG. 2, showing a graph of atrial and
ventricular depolarizations.
A peak detector 165 is coupled to sensing module 160 for detecting
the P-wave peak from the right atrium 115A, obtained by bipolar
sensing between electrodes 120 and 125 or by any other sensing
technique. The peak detector 165 also senses the R-wave peak at a
plurality of different sites associated with the left ventricle
115D, such as at each of the electrodes 130 and 135. In one
example, the electrode 130 is located near the left ventricular
apex and the electrode 135 is located near the left ventricular
base regions, i.e., closer to the left atrium 115C.
In another example, one of the two electrodes 130 and 135 (or an
additional third electrode) is located in a middle portion
("midregion") of the left ventricle 115D between the left
ventricular apex and the left ventricular base region. In another
example, the electrodes 130 and 135 are located in a middle cardiac
vein closer to a wall of the ventricle. Sensing at the electrodes
130 and 135 is either unipolar (e.g., the electrode 130 and/or 135
is sensed in combination with a relatively distant electrode, such
as one or both of housing electrode 150 and/or header electrode
155) or bipolar (e.g., the electrode 130 and/or 135 is sensed in
combination with another relatively close electrode, such as
another electrode disposed on the lead 110B and associated with the
left ventricle 115D, or another electrode disposed on the lead 110A
and associated with the right atrium 115A).
The system 100 may also include a telemetry transceiver 185
disposed in the device 105, which is communicatively coupled to an
external programmer 190. A time module 170 may also be included to
measure a time duration between various events, such as, for
example, the duration of time between adjacent contractions of the
heart 115.
The system 100 includes multiple therapy modalities. For example,
as discussed below, the system 100 may provide both bradycardia
therapy ("pacemaker mode"), as well as cardiac resynchronization
therapy ("CRT mode"). The mode in which the system 100 is currently
operating is termed the "operating mode." Although the example
embodiments illustrate two therapy modalities, other therapy
modalities may also be provided.
A controller 175 is provided to select an operating mode from among
the multiple therapy modalities. The controller 175 may select the
operating mode using one or more of the methods described below.
Once selected, the controller 175 communicates the operating mode
to a therapy module 180.
The therapy module 180 is coupled to electrodes 130 and 135 for
delivery of a desired therapy modality, specifically the therapy
modality associated with the selected operating mode, to the heart
115. The therapy module 180 is configured to deliver the desired
therapy modality using a plurality of operating parameters, as
described below.
B. Reuse of Operating Parameters
The operating mode for the system may be selected using both
automatic and manual methods, as disclosed below. Correct selection
of the operating mode can be important for several reasons,
including that operating parameters associated with the different
operating modes, as well as the goals of the therapies associated
with each operating mode, may differ significantly. An "operating
parameter" is a configuration variable associated with a specific
aspect of a given therapy controlling how the CRM device functions.
For example, an operating parameter may include a stimulation and
sensing configuration such as "VDD," which is a standard industry
convention for cardiac rhythm management systems. See, e.g., U.S.
Pat. No. 5,792,203 to Schroeppel. Although the two example therapy
modalities provided in the embodiment disclosed herein share some
of the same operating parameters and are implemented as a single
system, differences exist.
For example, Table 1 provided below illustrates some of the
differences for several operating parameters associated with
pacemakers and CRT devices, as are well known to those of ordinary
skill in the art.
TABLE-US-00001 TABLE 1 Typical Operating Parameters Associated with
Example Operating Modes Parameter Bradycardia-Pacemaker CHF-CRT
Device Stimulation/Sensing Mode DDD(R) VDD LRL 60 ppm 40 ppm Noise
Response DOO inhibit Atrioventricular Delay 120 ms 100 ms
As Table 1 illustrates, the operating parameters associated with
different therapies may vary significantly. For example, if the
device is operating in CRT mode, the device may include operating
parameters requiring the device to inhibit the delivery of
electrical impulses (i.e., Noise Response=inhibit) if interference
causes the device to lose atrial sensing, rather than to deliver
electrical impulses asynchronously, as this may decrease
hemodynamic performance. On the other hand, if the device is
operating in pacemaker mode, the device may include operating
parameters requiring the device to continue to deliver electrical
impulses (i.e., Noise Response="DOO" mode) asynchronously. Because
selection of the incorrect operating mode can actually decrease
hemodynamic performance, it is important to correctly determine
which therapy is appropriate for each patient.
Whenever possible, operating parameters that are common between a
CRT mode and a pacemaker mode are shared. As shown in FIG. 3, the
example controller 175 and therapy module 180 are illustrated in
greater detail. The therapy module 180 includes a pacemaker module
335, a CRT module 340, and operating parameters 311-317 associated
with the modules 335 and 340. The controller 175 includes an
operating mode selector module 355 coupled to the modules 335 and
340, as well as a protected memory module 360 and a detector module
370, both coupled to the operating mode selector module 355.
The pacemaker module 335 in this example embodiment is associated
with the plurality of operating parameters 311-314. The CRT module
340 includes the plurality of operating parameters 314-317. The
operating parameter 314 is common to both the pacemaker module 335
and the CRT module 340 and therefore is shared. However, other
operating parameters that are not common between the two modules
335 and 340 are maintained separately to avoid conflicts. For
example, the operating parameters provided in Table 1 differ and
therefore are not shared between the different modes. Further,
other operating parameters may be specific to one mode and
therefore would not be shared. For example, operating parameters
associated with implementing hysterisis may be relevant for
pacemaker mode but may not be relevant for CRT mode requiring
stimulation at regular intervals. However, other parameters, such
as stimulation amplitude and width, P- and R-wave sensing
sensitivity, antitachycardia response parameters, etc., may be
common to both modes.
C. Configuration of the CRM System
The therapy module 180 of FIG. 3 is further divided into two
hierarchical program levels to illustrate the programmable
capabilities of the cardiac rhythm management system 100.
Additionally illustrated in FIG. 3 are lower program level 310 and
higher program level 330. In order to manually program the system
100, a caregiver may utilize operating mode selector module 355 to
select between pacemaker module 335 and CRT module 340. Because
this selection is made in the higher program level 330, the
caregiver is allowed to simply select between the two modes, and
the system 100 automatically uses nominal operating parameters
associated with either the pacemaker mode or the CRT mode. For
example, if the operating mode selector module 355 is utilized to
select pacemaker mode, the associated nominal operating parameters
311-314 are utilized to configure the pacemaker module 335.
However, in some patients the nominal operating parameters will not
be sufficient to provide optimal hemodynamic benefits. In these
cases, the caregiver may further configure the individual operating
parameters associated with an operating mode. These modifications
are made in the lower program level 310, in which specific
operating parameters associated with the modules 335 and 340 may be
configured. For example, if the caregiver utilizes the operating
mode selector module 355 to select the pacemaker module 335, the
caregiver can configure operating parameters 311-314 to further
tailor the pacemaker module 335 to maximize hemodynamic benefits.
In this manner, the system 100 may provide ease of use by allowing
for selection between the pacemaker module 335 and the CRT module
340 in the higher program level 330, as well as provide for added
configurability by allowing for the modification of parameters
311-317 in the lower program level 310.
The operating mode selector module 355 of the controller 175 may
further utilize the detector module 370 to automatically select
between operating modes. The detector module 370 provides the
operating mode selector module 355 with physiological data
necessary to implement one or more of the methods described below
to automatically select between the two example operating modes.
This physiological data may be collected from the patient manually
or automatically by the system.
II. Example Methods Used to Select Between the Multiple Therapy
Modalities
Selection between the multiple therapy modalities may be automatic
or manual. Both automatic (i.e., can be performed by the system 100
without manual intervention) and manual methods for selection of
the operating mode are similar in that both may compare a patient's
hemodynamic response when operating in various therapy modalities.
For example, one or more methods may be used to determine whether
the CRM device operating in a first operating mode achieves a
better hemodynamic response than when operating in a second
operating mode.
For example, in the example method illustrated in FIG. 4, a
determination is made as to whether the application of cardiac
resynchronization therapy would be beneficial to the patient, as
shown in operation 410. If the application of cardiac
resynchronization therapy would result in the same or an increase
in hemodynamic performance, control is passed to operation 440, and
the CRM device is placed in CRT mode. Alternatively, if the
application of cardiac resynchronization therapy would result in a
decrease in hemodynamic performance, then control is passed to
operation 430 and the CRM device is placed in pacemaker mode. All
of the methods described below for selecting between the two
example modes may implement, at some level, the method as shown in
FIG. 4.
In FIG. 5, an example high-level operational flow 500 is provided
for a cardiac rhythm management system such as 100. At operation
510, the system is implanted into a patient using known techniques.
In conjunction with, or possibly after implantation, control is
passed to operation 520, where a determination is made as to the
appropriate therapy to provide to the patient. In the example
embodiment, the operation 520 selects between multiple therapy
modalities that may be delivered to the patient for treatment of an
arrhythmic condition.
In the illustrated method, the therapies include bradycardia
therapy (pacemaker mode) and cardiac resynchronization therapy (CRT
mode), although other therapies may also be provided. In addition,
within each therapy modalities (i.e., the pacemaker mode and the
CRT mode), a plurality of sub-therapy modalities can be provided
such as, for example, multiple therapies that can be administered
to remedy bradycardia.
Selection of the appropriate therapy modality can be achieved
manually, using, for example, the external programmer 190 (see,
e.g., FIG. 1). Alternatively, the controller 175 may automatically
select between pacemaker mode and CRT mode using one or more of the
methods described below.
If the therapy modality selected is pacemaker mode, control is
passed to operation 530 and the system functions as a state of the
art pacemaker with all associated modalities. Alternatively, if the
CRT mode is selected, control is passed to operation 540, and the
system functions as a state of the art CRT device.
A variety of methods may be used to make the selection in operation
520, as described below.
A. Q*S* Method
In U.S. patent application Ser. No. 10/008,397, filed on Dec. 6,
2001 and entitled "IDENTIFYING HEART FAILURE PATIENTS SUITABLE FOR
RESYNCHRONIZATION THERAPY USING QRS COMPLEX WIDTH FROM AN
INTRACARDIAC ELECTROGRAM," incorporated by reference herein in its
entirety, a method is described for identifying patients who may
benefit from cardiac resynchronization therapy through analysis of
the duration of ventricular depolarization, or the width of the QRS
complex, measured intracardially. According to the method, an
intracardiac electrogram is digitalized and smoothed using a
rectangular moving window. The time of peak depolarization (R) is
determined and the absolute derivative of the waveform is
calculated. Next, the maximum absolute derivative before R
("max-BR") and after R ("max-AR") are determined. The Q* point is
the first point before R at which the absolute derivative is
approximately 2% of max-BR, and the S* is the first point after R
at which the absolute derivate is approximately 10% of max-AR. The
Q*S* interval is then compared to a threshold value. If the
duration is greater than or equal to the threshold, the patient is
labeled a responder to cardiac resynchronization therapy and, in
operation 520, CRT mode is selected. Alternatively, if the duration
is less than the threshold, pacemaker mode may be used. In one
embodiment of the method, the threshold is set at approximately 170
milliseconds. Other durations, as well as other threshold values,
may also be used.
B. Interval between Q-Wave-LV (Lead) Method
Another method that may be employed to select an operating mode for
the CRM device includes measurement of a duration of the onset of
ventricular depolarization measured from either a surface ECG or
left ventricular intracardiac electrogram to the peak of the
left-ventricular intracardiac electrogram at the stimulation site
(the "Q-wave-LV interval"). This Q-wave-LV interval is measured,
and the duration is compared to a threshold value. If the duration
is greater than or equal to the threshold, the stimulation site is
labeled a responder site to cardiac resynchronization therapy and
CRT mode is selected. Alternatively, if the duration is less than
the threshold, pacemaker mode may be used. In one embodiment of the
method, the threshold is set at approximately 80 milliseconds if Q
is measured from a surface ECG and 100 milliseconds if Q is
measured intracardially. Other threshold values may also be
used.
C. Surface QRS Wave Method
Another method that may be employed to select an operating mode for
the CRM device includes measurement of a duration of ventricular
depolarization, or the QRS complex, at the surface of the patient
(i.e., intercardially) and comparison of that duration to a
threshold value. If the duration is greater than or equal to the
threshold, the patient is labeled a responder to cardiac
resynchronization therapy and CRT mode is selected. Alternatively,
if the duration is less than the threshold, pacemaker mode may be
used. In one embodiment of the method, the threshold is set at
approximately 150 milliseconds. Other threshold values may also be
used.
D. Interventricular Pressure Method
Another method that may be employed to determine a correct
operating mode for the system is generally described in U.S. Pat.
No. 6,280,389 to Ding et al., incorporated by reference herein in
its entirety. This method involves measurement of a patient's left
and right ventricular pressure for a specified period of time using
a pressure-measuring device. A normalized pressure loop area for
each heartbeat measured is then calculated and a mean pressure area
determined. This mean pressure area is then compared to a threshold
value to determine whether the patient is a responder. If the area
is equal to or greater than the threshold, the patient is labeled a
responder, and CRT mode is selected. Alternatively, if the area is
less than the threshold, pacemaker mode is selected. In an example
disclosed in the patent, the threshold is set to 0.3.
E. Paced QRS Method
Another method that may be employed to determine a correct
operating mode for a CRM system is generally described in U.S.
patent application Ser. No. 09/822,790, filed on Mar. 30, 2001 and
entitled "METHOD AND APPARATUS FOR PREDICTING ACUTE RESPONSE TO
CARDIAC RESYNCHRONIZATION THERAPY," incorporated by reference
herein in its entirety. The method generally described in this
application involves measuring a first interval during an intrinsic
systolic cycle, measuring a second interval during a
stimulation-induced systolic cycle, and comparing a percentage
change in duration between the first interval and the second
interval against a pre-determined threshold. The interval disclosed
is a patient's intrinsic ventricular depolarization, although other
intervals may also be used. If the percentage change is equal to or
less than the threshold, disclosed as between 10-25 percent, then
the patient may be labeled a "responder" and the CRM device may be
set to perform in CRT mode. Alternatively, if the percentage change
is greater than 10-25 percent, then the CRM device may be set to
perform in pacemaker mode.
As previously indicated, the determination made in operation 420
may be automatically made by a CRM system using one or more of the
methods described above, or other similar methods. Further, the
operating mode may be manually selected by a caregiver and the CRM
system manually programmed.
F. Automatic Reconfiguration Method
A method 600 according to another embodiment of the invention is
illustrated in FIG. 6. The method 600 is similar to the method 500
illustrated in FIG. 5, except that once the operating mode has been
selected by operation 620, control is periodically passed back to
operation 620 to make a new determination of the correct operating
mode. The device may be set to make this new determination at
certain intervals, such as daily or weekly, or the device may be
set to make this new determination after a certain event has
occurred, such as the failure to sense an intrinsic wave (e.g., an
R-wave) after a given interval. In this manner, a CRM system
implementing the method 600 periodically reevaluates and adapts to
a patient's needs as the patient's needs change. For example, a
patient receiving bradycardia pacing support may develop a need for
CRT therapy as the patient's needs change. In method 600, the CRM
system may automatically detect this change in the patient's needs
and switch from pacemaker mode to CRT mode or vice versa.
III. Example Reversion Management System
Another aspect of the invention is a reversion management system.
The reversion management system generally includes a protected
memory module 360, shown in FIG. 3, to store one or more operating
parameters associated with an operating mode. The one or more
operating parameters stored in the protected memory module 360 are
collectively referred to herein as a reversion mode. During typical
CRM system operation, several different environmental conditions
may disrupt normal CRM system performance. Such conditions may
include high power antennas for radio broadcasting, anti-theft
devices used in convenience stores entrances, electrosurgery
conducted on the patient, or other such electrical or magnetic
interference that may disrupt normal operation. The reversion mode
provides the necessary operating parameters associated with the
correct operating mode should normal device operation be
disrupted.
The protected memory module 360 is a protected memory space based
on a specialized hardware design. Typically, an 8-bit memory has a
3-bit parity check associated with it, so that any of the 8-bits
can be restored if corrupted. Hamming error correction may also be
used to ensure that the memory module 360 is free from
corruption.
A method 700 illustrated in FIG. 7 shows an example operational
flow for the reversion management system. In operation 710, a CRM
system determines whether it is currently operating in pacemaker
mode or CRT mode. If the CRM device determines that the operating
mode is pacemaker mode, control is passed to operation 720, and the
operating parameters associated with the pacemaker mode are stored
in a protected memory module. Alternatively, if the CRM device
determines that the current operating mode is CRT mode, control is
passed to operation 730, and the operating parameters associated
with the CRT mode are stored in the protected memory module. The
reversion mode stored in the protected memory module may be updated
periodically, such as daily or weekly, so that the most current
operating parameters associated with the operating mode are stored
in the protected memory module.
The operating parameters stored in the protected memory module may
be nominal operating parameters associated with a typical pacemaker
or CRT device, or may be the actual parameters associated with an
operating mode. For example, nominal operating parameters for a
pacemaker mode may be sufficient for most patients exhibiting
bradycardia because of the rather homogeneous clinical indications
associated with bradycardia. Therefore, nominal values may, but
need not, be stored in the protected memory as the reversion mode
if the device is operating in pacemaker mode. On the other hand,
CRT patients typically are not homogenous and therefore require
operating parameters adapted individually for each patient.
Therefore, actual operating parameters associated with the CRT mode
may be stored in the protected memory as the reversion mode.
An example operational flow 800 shown in FIG. 8 illustrates how a
CRM device may utilize a reversion mode stored in a protected
memory to recover from a disruption. In operation 810, the CRM
device is functioning normally in an operating mode. In 820, a
disruption to the CRM device occurs, such as from one of the
external conditions described above. After the CRM device recovers
from the disruption, in operation 825 the CRM device determines
whether a reversion mode has been stored in the protected memory.
If no reversion mode has been stored in protected memory, control
is passed to operation 826 and nominal operating parameters are
used. However, if a reversion mode has been stored, control is
passed to operation 830 and the CRM device accesses the reversion
mode stored in the protected memory. Finally, in operation 840, the
CRM device resets the operating mode based on the reversion mode to
allow the CRM device to function in a manner similar to that before
the disruption.
Therefore, in this manner, the CRM device may recover from a
disruption and continue to provide beneficial therapy to the
patient. The reversion mode allows the CRM device to use the
correct operating parameters and continue to operate correctly
after a disruption to the CRM device occurs.
The embodiments of the invention described herein may exhibit
several advantages over prior devices. The CRM systems disclosed
herein provide a plurality of therapy modalities, rather than a
single therapy. In this manner, costs associated with product
development are reduced. Further, because the CRM system may be
reprogrammed while ambulatory to provide different therapies, the
device may adapt to a patient's needs as the patient's needs change
over time. In addition, because the device is reprogrammable,
operating parameters associated with the operating mode may be
tailored to provide optimal hemodynamic benefits. Also, a CRM
device implemented according to the invention may automatically
select the operating mode and thereby reduce or eliminate errors
made by a caregiver in the selection of an appropriate operating
mode and may continue to provide optimal therapy to the patient
even after recovery from a disruption.
The methods of the present disclosure can be implemented using a
system as shown in the various figures disclosed herein comprising
various devices and/or programmers, including implantable or
external devices. Accordingly, the methods of the present
disclosure can be implemented: (1) as a sequence of computer
implemented steps running on the system; and (2) as interconnected
modules within the system. The implementation is a matter of choice
dependent on the performance requirements of the system
implementing the method of the present disclosure and the
components selected by or utilized by the users of the method.
Accordingly, the logical operations making up the embodiments of
the method of the present disclosure described herein can be
referred to variously as operations, steps, or modules. It will be
recognized by one of ordinary skill in the art that the operations,
steps, and modules may be implemented in software, in firmware, in
special purpose digital logic, analog circuits, and any combination
thereof without deviating from the spirit and scope of the present
invention as recited within the claims attached hereto.
The present invention should not be considered limited to the
particular examples described above, but rather should be
understood to cover all aspects of the invention as fairly set out
in the attached claims. Various modifications, equivalent
processes, as well as numerous structures to which the present
invention may be applicable will be readily apparent to those of
skill in the art to which the present invention is directed upon
review of the instant specification.
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